The importance of water purification is expanding as the condition of water supplies becomes increasingly polluted. Many bodies of water have become contaminated to a degree in which the water is not useable unless it is first purified to remove contaminants. The demand for purified water has also increased in recent years as consumers become more health-conscious. The quality of drinking water is coming under closer scrutiny, as evidenced by the popularity of brand-name bottled waters.
Portable, refillable water bottles have also become increasingly popular. These bottles are designed to contain a variety of fluids, from plain water to exotic sports drinks. These bottles typically include a resealable cap and a straw for transferring the liquid to the user's mouth. When the bottle is empty, the user frequently desires to refill it with purified water. However, a source of purified water is not always available, for example when the user is traveling, exercising, hiking, biking, or camping, or in emergency situations. Frequently, the water that is available is contaminated and must be purified before it can be consumed.
Several methods of purifying water are available. Purification tablets are inconvenient and give the water an undesirable flavor. Purification of water by boiling is time-consuming and a source of heat may not be available. Typical filtering devices that utilize pumps are bulky, heavy and not designed to be portable.
U.S. Pat. No. 4,995,976 to Vermes et al. discloses a portable water purification device in the form of a straw through which water can be drawn by a user. The interior of the tube is filled with filtering materials to remove contaminating substances, such as dirt, sediment, and bacteria.
U.S. Pat. No. 4,298,475 to Gartner discloses a tubular portable water purification system. The devices of Vermes et al. and Gartner are not capable of removing small parasites 1-2 .mu.m in size.
It is an object of the invention to provide a portable water purification device that is designed to kill viruses and bacteria present in the water to be purified. Another object of the invention is to provide a portable water purification device that is designed to remove exceedingly small microorganisms, such as potentially harmful parasites 1-2 .mu.m in size, from the water to be filtered. Yet another object of the invention is to remove Cryptosporidium from the water to be purified. Yet another object of the invention is to provide a device including a microfiltration membrane that excludes microorganisms as small as 1-2 .mu.m in size without substantially restricting the flow rate of water through the device.